JPH04299632A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To set a duty ratio of an output signal to 50% when an inputted sinusoidal wave signal is in existence by not sending an erroneous signal to a post-stage circuit connecting to an output of the waveform shaping circuit so as to prevent malfunction. CONSTITUTION:A rectangular waveform shaping circuit 103 receives a sinusoidal wave signal 1 as an input signal and outputs a rectangular wave signal 2. A bias circuit 102 gives a bias to the sinusoidal wave signal 1. A signal interrupt detection circuit 104 detects the interrupt of the sinusoidal wave signal 1. An output signal control circuit 4 uses a detection signal 3 of the signal interrupt detection circuit 104 to stop an output 4 of a rectangular wave signal 2 outputted by the rectangular waveform shaping circuit 103.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform shaping circuit used in digital transmission equipment, and more particularly to a waveform shaping circuit for rectangular waves.

0002

2. Description of the Related Art FIG. 3 is a block diagram of a conventional waveform shaping circuit for rectangular waves, and FIG. 4 is a diagram showing a specific example thereof. This will be explained below using FIGS. 3 and 4.

The conventional waveform shaping circuit includes a rectangular wave shaping circuit 103 that inputs a sine wave signal 1 and outputs a rectangular wave signal 2 using an IC gate, and a rectangular wave shaping circuit 103 that inputs a sine wave signal 1 and outputs a rectangular wave signal 2 using an IC gate, and a rectangular wave shaping circuit 103 that inputs a sine wave signal 1 and outputs a rectangular wave signal 2 using an IC gate. The bias circuit 102 provides a threshold level for the IC of the circuit 103.

Next, the operation will be explained. A bias at the same level as the threshold level of the IC is applied to the input of the rectangular wave shaping circuit 103, and the sine wave signal 1 is input. The rectangular wave shaping circuit 103 performs waveform shaping of the rectangular wave rather than the sine wave by outputting "High" if the input sine wave signal 1 is greater than the threshold level, and outputting "Low" if it is smaller.

[0005]

In the conventional waveform shaping circuit, in order to set the duty ratio of the rectangular wave signal 2 to 50%, the bias applied to the sine wave signal 1 must be made the same as the threshold level of the IC. Since the threshold level of an IC has a certain uncertainty width, a gate IC outputs a noisy signal when the input is fixed at this level. Therefore, when the input sine wave signal 1 is disconnected, the input of the rectangular wave shaping circuit 103 is fixed at the threshold level of the IC, so a noisy rectangular wave is output, and the output of this wave shaping circuit is There was a problem in that the rear circuit connected to the side could malfunction due to erroneous signals.

[0006] Furthermore, if the bias applied to the sine wave signal 1 is set away from the threshold level of the IC,
When the input sine wave signal 1 is disconnected, the rectangular wave signal 2 is not output as the output of the rectangular wave shaping circuit 103, but when it is normal, there is a problem that the duty ratio of the rectangular wave signal 2 does not become 50%. Ta.

[0007]

[Means for Solving the Problems] The waveform shaping circuit of the present invention includes a rectangular wave shaping circuit that receives a sine wave signal as an input signal and outputs a rectangular wave signal, and a bias circuit that biases the input sine wave signal. , a configuration comprising: a signal disconnection detection circuit that detects disconnection of the sine wave signal; and an output signal control circuit that stops outputting the rectangular wave signal output by the rectangular wave shaping circuit in response to a detection signal of the signal disconnection detection circuit. Further, the waveform shaping circuit of the present invention includes a rectangular wave shaping circuit that receives a sine wave signal as an input signal and outputs a rectangular wave signal, a signal disconnection detection circuit that detects disconnection of the sine wave signal, and a signal disconnection detection circuit that detects disconnection of the sine wave signal. The present invention may also include a bias circuit that applies a bias to the sine wave signal by varying the bias level based on the output signal of the circuit.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, the waveform shaping circuit includes a rectangular wave shaping circuit 103 that inputs a sine wave signal 1 and outputs a rectangular wave signal 2 using an IC gate;
A bias circuit 102 that applies a bias to the sine wave signal 1, a signal disconnection detection circuit 104 that detects disconnection of the sine wave signal 1, and an output signal control circuit 101 that controls the output of the rectangular wave signal.

The operation will be explained below. Bias circuit 1
02 applies a bias of the same level as the threshold level of an IC (not shown) of the rectangular wave shaping circuit 103 to the sine wave signal 1, and the sine wave signal 1 is input to the rectangular wave shaping circuit 103. The rectangular wave shaping circuit 103 performs waveform shaping by outputting "High" if the sine wave signal 1 is greater than the threshold level, and outputting "Low" if it is smaller.

The signal disconnection detection circuit 104 determines the level of the sine wave signal 1. The determination of the level is performed in an analog manner by predetermining a value smaller than the value at which it can be confirmed that the sine wave signal 1 is sufficiently large and larger than the noise level as a determination value, and comparing this with the sine wave signal 1.

The output signal control circuit 101 converts the rectangular wave signal 2 from the rectangular wave shaping circuit 103 into the output rectangular wave signal 4 in response to the signal disconnection detection signal 3 which is the output of the signal disconnection detection circuit 104.
It may or may not be output as . Here, if the input sine wave signal 1 is disconnected, the rectangular wave shaping circuit 10
3 and the signal disconnection detection circuit 104 have only the bias level input. The signal loss detection circuit 104 detects that the level of the sine wave signal 1 is smaller than the determination value, and outputs the signal loss detection signal 3. The output signal control circuit 101 stops outputting the output rectangular wave signal 4 in response to the signal disconnection detection signal 3. As a result, when sine wave signal 1 is input, 5
The output rectangular wave signal 4 can be output with a duty ratio of 0%, and when the sine wave signal 1 is cut off, no noisy rectangular wave is output to the rear circuit.

The same applies to the case where the output of the waveform shaping circuit is directly controlled by the output of the signal disconnection detection circuit.

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which a bias circuit 105 is controlled by a signal loss detection signal 3 which is an output of a signal loss detection circuit 104, and the bias voltage is changed to a rectangular wave shaping circuit. By shifting the threshold level of the IC 103 (not shown) from a predetermined value, results equivalent to those described in the first embodiment can be obtained.

It goes without saying that the present invention can also be applied to a waveform shaping circuit that converts an analog signal into a unipolar signal.

[0016]

[Effects of the Invention] As explained above, the present invention is configured so that when the input sine wave signal is disconnected, this is detected and the output of the waveform shaping circuit is stopped by this signal disconnection detection signal. This has the advantage of not transmitting erroneous signals to the rear circuit, preventing malfunctions, and setting the duty ratio of the output signal to 50% when there is an input sine wave signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the invention.

FIG. 3 is a block diagram of a conventional waveform shaping circuit.

FIG. 4 is a diagram showing a specific example of FIG. 3;

[Explanation of symbols]

101 Output signal control circuit 102, 105 Bias circuit 103 Square wave shaping circuit 104 Signal disconnection detection circuit

Claims (2)

[Claims] 1. A rectangular wave shaping circuit that receives a sine wave signal as an input signal and outputs a rectangular wave signal, a bias circuit that applies a bias to the input sine wave signal, and a signal disconnection circuit that detects disconnection of the sine wave signal. A waveform shaping circuit comprising: a detection circuit; and an output signal control circuit that stops outputting a rectangular wave signal output by the rectangular wave shaping circuit in response to a detection signal from the signal disconnection detection circuit. 2. A rectangular wave shaping circuit that receives a sine wave signal as an input signal and outputs a rectangular wave signal, a signal disconnection detection circuit that detects disconnection of the sine wave signal, and a bias level determined by the output signal of the signal disconnection detection circuit. a bias circuit that applies a bias to the sine wave signal by varying the sine wave signal.